On Wed, 13 Aug 2003 20:55:09 -0300, you wrote:
Interesting note here on speed. Early on I was told that flashcut had a
problem with threading above a certain speed, so I tried to design the
compensator to allow any speed. This is, of course, impossible, but I am
interested in any experience in this area. The technique is a little unique.
I use a bresenham algorithm within the main bresenham algorithm to slow down
time if the spindle slows. The design assumes the spindle will not speed up
above the starting RPM during a thread (hopefully a good assumption) so time
simply slows down for the pulser which has already computed the pulse timing
using the original algorithm based on the originating spindle speed
feedback. This time slowing is done useing a time constant derived on each
revolution as the adder to the bresenham. There is no way that one pulse per
rev can do the job in the end I think, but I am interested in how fast
anyone CAN do a thread using this technique.
The old controller was quite happy to thread all the pitches I tried
at between 500-800 rpm, with it's limits of 1100rpm top speed, and max
400mm/min axis speed I thought it was pretty good. It was remarkably
accurate too with only one pulse per rev.
I think the limitations in this case were down to a 2Mhz processor and
OS, rather than lathe hardware.
This algorithm within an algorithm was the only way I could think of to
do this reliably in a buffered pulse engine, the results will be
interesting.
How is your basic? That's what the old program was written in <G>. If
you understand it, it may be worth a look to see how it was done?
I think I can retrieve it off the 5 1/4" floppies (If the drive I have
still works).
To see your theoretical maximum thread pitch at any speed easily , you need
only set a spindle speed, and then jog back and forth in the Z axis.
I'll have a play tomorrow and report back.
--
Steve Blackmore
